Safety spring-sling particularly adapted for use with parachutes



E. R. CALTHROP. I SAFETY SPRING SLING' PARTICULARLY ADAPTED FOR USE WITH PARAC HUTES.

APPLICATION FILED JULY 3h I-9l8.

Patented Dec. 20', 1921.

ivar ara' Elk/ igid (Hire v IAWBY JP flier/my UNITED STATES EVERARD RICHARD CALTEROP; OF LONDON, ENGLAND, ASSIGNOR TO E. R. GALTHROPS PATENT OFFICE.

AERIAL PATENTS -LIMITED, LONDON, ENGLAND.

sum? srmnc snmc PARTICULARLY anarrnn non. use wrrn rmcmrrns- Specification of Letters Patent.

Patented Dec. 20, 1921.

Application filed 1111 31, 1918. Serial No. 247,508.

(GRANTED UNDER THE PROVISIONS OF THE ACT 0]? MARCH 3, 1921,}1 STAT. L, 1818.)

adapted for use with parachutes same comprising a shock absorbing device for use by aviators when making a descent from an air craft by means of a parachute and consisting essentially of a resilient'and extensible element mounted between the parachute and the passen er and an inextensible flexible element 0 greater length than the re silient and extensible element at rest.

Such a shock absorbing device possesses great advantages in use but when the same is partly composed of ordinary laid rope 1t has usually been found that in actualpractice the aviator is liable to experience some discomfort due to the spinning or twisting of the aforesaid rope owing to the uncoiling and recoiling of the, laid strands thereof.

Now the primary object of the present invention is to render the construction bereft "of any bias or tendency to spin or twist in any direction when theweight or load is applied, and to simplify and generally improve the constrfiction whereby the device is rendered more efficient for the ends in view.

.Accordingto this invention in order to effect the objects aimed at instead of employing ordinary laid rope a rope is used in which the fibers thereof are plaited or braided or this plaitedrope may be tubular with one or more tubular plaited ropes each within the next or I may employ a plurality of lengths of diagonally woven webbing stitched together or agaln I may use two ordinary laid ropes connected together at intervals said ropes being preferably 131d in opposite directions that 1s to say right and left hand laid ropes.

As is well known an ordinary rope readily lends itself to splicing and the necessary stituted loops or eyes in the device are conveniently formed in that manner but it is not feasible to produce a satisfactory splice in a plaited or bralded rope and when employing this material I contemplate forming the necessary eyes or loops by knotting the rope and I have found that the most satisfactory knot is that known as a bowline knot but even a knot of this character is liable when unloaded to slacken under vibration and shocks and t0 'shp when strain is exerted upon it and I therefore employ means whereby in all circumstances the knot is kept taut. This 1s effected by providing a sleeve of suitable material such as rubber or the like which is passed over the knot and I have found that no matter what vibration shocks or v arying stralns the rope is subjected to a lbowline knot so confined will remain taut.

The resilient and extensible element which 1s adapted to be placed in tension when the load 1s applied is constituted by a number of strands of rubber which are twisted together 'IIIOPPQSl-llg spirals in such a manner that the 1nd1v1dual strands are not shortened so that when the composite element thus con- 1s placed in tension an equal strain will be borne by eachv spiral and by each of the strands.

In order that the invention may be readily .understood and carried into effect same will now be described more fully with reference to the accompanying drawings in which:

Flgure l is a general view illustrating the I complete safety spring sling attached to a parachute.

F1g. 2 illustrates diagrammatically the type of rope employed.

F g. 3 1s a view ofthe resilient and extenslble element thereof detachedand drawn to a larger scale the strands on one side be- 1 gsomewhat distorted from their normal position represented on the other side of the figure in order to show the arrangement of unshortened strands.

Fig. 4 is a view showing the form of knot known as a bowline knot'used in constructing the eyes or loops for carrying the resilient and, extensible element.

Fig. 5 represents a modified form of the resilient and extensible element of the improved sling.

In' carrying out the invention the rope 1 whihh is preferably continuous so as to furnish the loops or yoke pieces 2.2. for carry ing the stranded resilient and extensible element 3 is formed of plaited or braided strands of fiber hemp or other appropriate material and may be solid or it may as shown in Fig. 2 be constituted by a plurality of tubular portions f, g and a solid portion it one within the other. By using a rope of this construction the spinning or twisting incidental to the employment of the ordinary laid rope is entirely obviated. In-

stead of the plai'ted or braided form of rope a plurality of lengths of diagonally woven webbing stitched together may be employed or two ordinary oppositely laid ropes may be used same being connected together at intervals in their length. .I have found however that good results are insured by the employment of the plaited or'braided form of rope above described and illustrated in the drawings.

In order to provide for the necessary eyes or loops for carrying the aforesaid resilient and extensible element 3 and the safety hooks 4, 5 for attachment respectively to the rigging p of the parachute P (not shown) and the aviators. harness (not shown) the said rope I is knotted into what are known as bowline knots. The knots 6, 7 furnish the eyes or loops 2, 2-for the ends of the element 3 while the knots 8, 9 furnish the loops 10, 11 for the safety hooks 4, 5 respectively.

The portion 120i the rope between the knots 6, 7 serves as a safet rope in the event of .the element 3 'brea 'ng from any cause taut condition I have found that sleeves such as indicated at 13, 14, 15' and 16 when formed of resilient material such as rubber or the like and passed over the knots enable the latter 'to disintegration andF'to preserve their tautne fl yhatever the nature of the vi bration shockor varying strains to whichthe rope may be subjected.

As will be seen in Fig. 4. which is a damn view of the knot 7 the bowline knot is made by first forming the loop 17 and the loop 2 then placing the rope aboutthe aforesaid loop 17 to form the encircling coil 18 and lastly drawing the end of the. coil through the loop 17. n

The esilient and. extensible element 3- is composed ;pf strands of rubber adapted to be placed in tension upon the application of theload. The several strands constituting the resilient and extensible elements are" twisted together in opposing spirals as shown in Fig. 3 the several strands being of uniform length and the arrangement on the loop 2 being such that the strain when the element is subjected totension is borne equally byjall and each-of the strands. In the example illustrated it will be observed that the element is composed of two series of -five strands whereof the twist or spiral is in oppositedirections. The dispositlon of the respective strands a, b, a, d and e, is such that say: the strand a which in: the upper loop 2 assumes the outermost and uppermost position'in regard to the curve of the loop if traced through the spiral will be I found to; assume the innermost gr approximately central position of the curve of the lower loop'2. The strand b which is disposed inithe next outermost position in regard to the upper loop 2 similarly assumes the next innermost position in regard to the curve of the lower loop 2. The relative positions ofthe stands cand d may similarly be traced and the strand e which occupies the innermost position inregard to the curve of the upper loop 2 assumes the outermost 1 position in regard to the curve ofthe lower loop 2. the figure are shown as spread out toward the loops 2, 2.in order to clearly. illustrate the above described arrangement whereby the individual strands are not shortened;

the natural or normal twist or attitude of the several strands relatively to each other In Fig. 3 the strandson the left of I is shown on the right hand side of the figure and it strain is distributed equally upon each spiral and upon all of the strands.

I claim:---

1. The crimbination, with a parachute, of a safety spring sling or suspension device comprising an inextensible, flexible element extending in a single unitary piece from theparachute to the passengers harness, a plurality ofq'springs normally of less length than said inextensible element, said sprmgs being so-constructed as to prevent spinning and twisting when weight is applied, at-- taching means on the inextensible element to which the opposite ends of the springs are connected, and means directly engaged with said attaching means to prevent displacement thereof. I

2. The combination, with a parachute, of

will be readily seen that the a safety spring sling or suspension device spinning" and twistthe opposite ends of the springs, and means structurally separate from said looped portions directly engaged with the same to prevent them from becoming displaced.

3. The combination with a parachute of a safety spring sling or suspension device comprising a plurality of springs so constructed as to prevent "spinning and twisting when weight is applied, means for mounting the said springs between the parachute and the passenger, a continuous inextensible flexible element constructed, of plaited or braided rope of greater length than said springs at rest, eyes or loops formed by knotting said element, and sleeves of resilient material inclosing said knots.

4. The combination with a parachute of a safety spring sling or suspension device comprising a resilient and 'extensible element composed of a plurality of strands of rubber arranged in opposing spirals to cause the strain to be borne equally by each spiral and by all of the strands, means for mounting the said element between the parachute and the passenger, a continuous inextensible flexible element constructed of plaited or braided rope of greater length than said resilient and extensible element at rest, eyes or loops formed by knotting said inexmounting the same between the parachute and the passenger, a continuous inextensible flexible element constructed of plaited or braided rope of greater length than said springs at rest, eyes or loops formed by knotting said element to receive said springs and sleeves of resilient material inclosing said knots.

6. The combination with-a parachute of a safety sprlng sling or suspension device comprising a plurality of springs composed of strands of rubber arranged in opposing spirals, a continuous inextensible flexible element constructed of plaited or braided rope of greater length than said springs at rest, means for mounting said springs on the said inextensible element so that the strain is borne equally by each spiral and by all of the strands, knots in said inextensible element'and a safety loop formed element.

E. R. CALTHROP.

in said inextensible 

